What cart. for the Reed 3P?

Like Chakster implied, it depends on the effective mass of the Reed what one would recommend, because each Reed can be had in something like six different species of wood that vary quite a bit in density.  I have a Red Cedar 10.5-inch Reed 2A (about 12-15g effective mass) currently running a Stanton 980LZS, which sounds so good that I have been too lazy to try anything else for nearly a year now.

Raul, (1) I have removed the brush entirely from my 980LZS. This probably reduces its weight by 2-3 gm. (It would be interesting to know the exact weight of the brush assembly.) And (2) with age, it is quite likely that the actual compliance of the 980LZS is lower than factory spec.

Both of these factors would tend to increase the resonant frequency somewhat, perhaps into a more acceptable zone.  As you said, it does work well, regardless.

I wrote elsewhere that I mounted an Acutex LPM320 (Compliance = 42) on my FR64S with Dynavector headshell, and amazingly there is NO problem with resonant frequency.  If the FR64S + headshell + Acutex has a collective effective mass of 30g, then the predicted RF is ~5 Hz.  My guess is that the Acutex has lost compliance.  (On the other hand, it tracks piano as well as or better than any other cartridge I own.) I do take you seriously as regards your reservations about the FR tonearms, but this combo sounds superb, much to my surprise.

Please stop with the bit about distortion on tube electronics.  It would be inappropriate to reply here, but suffice to say that what you say applies to transformer coupled tube amplifiers, not to any other form of tube gear.  Well done tube preamplifiers and OTL amplifiers can compete with solid state for bench measurements, if indeed I believed those mean much.  Further, the only way solid state gets to really low numbers is by use of gobs of NFB, which generally is a cure worse than the disease.

Thoughts on pairing the Reed with the SME turntable(s):  Just do it.  The interaction of a tonearm with a turntable is much less significant than the complex interactions among the mat, the tonearm, and the cartridge, each with the other two.  In jiggly sprung turntables like the Linn or maybe the Oracle, then you have to worry about tonearm weight per se, only because very high or very low weight will upset the suspension.